1. Field of the Invention
The present invention relates to techniques for communicating signals between electrical circuits. More specifically, the present invention relates to a method and an apparatus for performing differential signaling through parallel communication channels in a manner that reduces coupling noise between nearby communication channels.
2. Related Art
As processor clock speeds continue to increase at an exponential rate, it is becoming increasingly harder to communicate signals between computer system components in a manner that meets bandwidth requirements. In order to achieve high bandwidth, systems typically route signals through a number of communication channels in parallel. (Note that these parallel communication channels typically use electrical, capacitive, inductive or optical signaling.) Many systems additionally use differential signaling techniques, in which complementary pairs of signals are communicated through parallel communication channels.
These parallel communication channels are typically packed into a small area to achieve high bandwidth within a small cross-sectional area. Unfortunately, packing channels together leads to “coupling” between neighboring communication channels. This coupling introduces noise, which reduces the signal-to-noise ratio in the communication channels and thereby adversely affects communication through the communication channels.
Existing systems solve this coupling problem in a number of ways. Physical separation can be introduced between communication channels. However, introducing physical separation can significantly increase the cross-sectional area used for communication. Grounding planes between can be inserted between electrical, capacitive or inductive communication channels. Such grounding planes protect the communication channels from noise. However, they also introduce parasitic capacitances that can retard and attenuate signals that pass through the communication channels.
Hence, what is needed is a method and an apparatus that facilitates differential signaling through parallel communication channels in a manner that reduces coupling noise between nearby communication channels.